Well put, Folk1234. I guess what got me ranting, was that Conrad is putting all house concerts in the worst possible light, by getting the 2 kinds of events mixed up, perhaps from experience, but it must be a very limited experience.
I'm sure the vast majority of house concerts which charge a fee, are publicized, open to the general public, start at a standard concert time, include around 90 minutes of fairly formal performing time, & give 90 - 100% of the admission fee to the performer. And most of these house concerts are a very significant portion of the performers' annual income, & sometimes the entire income for a tour where the performer is not well known, or plays to a small but devoted following.
I'm sure the vast majority of post-concert concerts are as described above by Folk1234, & are free & informal. Most performers don't hawk their wares at more party-like events, but are sometimes asked by attendees who didn't make it to the sales table of the formal concert, to sell a few items. As to being egalitarian & "jamming with the ordinary folk", that depends on the personality & energy level of the performers, who come in as many varieties as members of any other profession.